Coupling with quick release valve

ABSTRACT

A drive for transmitting torque from a driving to a driven member includes an inflatable member which is adapted to connect the driving and driven members when inflated by a fluid under pressure. The drive includes a valve assembly having an inlet connected to a fluid supply, a first outlet in communication with the inflatable member and a second outlet for venting the inflatable member. The valve assembly has a movable one-piece valve member which has a first position for restriciting fluid flow between the inlet and the first and second outlets while providing for fluid communication between the first and second outlets. When fluid is supplied under pressure to the inlet, the valve member has a surface area against which the fluid acts to move the valve member from the first position to a second position. In the second position, the valve member restricts fluid flow between the first and second outlets while providing for fluid communication between the inlet and the first outlet which effects inflation of the inflatable member, resulting in the driving and driven members being drivingly connected thereby. A muffler may be utilized in connection with the second outlet to control the level of noise associated with the operation of the valve.

United States Patent [191 Roob [ 1 May 22, 1973 [21] Appl. No.: 127,691

[52] US. Cl ..192/88 B, 192/106 F, 303/69,

l37/625.68,137/102 [51] Int. Cl ..Fl6d 25/04 [58] Field of Search..192/106 F, 88 A,

192/88 B, 12 C, 18 A, 85, 85 AA; 303/69; 137/102, 107

[56] References Cited UNITED STATES PATENTS 3,480,121 11/1969 Maigrot..l92/l8 A 2,277,554 3/1942 McCoy ....192/l06 F 2,706,487 4/1955Wilson.... ..303/69 X 2,718,897 9/1955 Andrews ..303/69 X 2,909,256l0/l959 Chung ..l92/l06 F Primary Examiner-Benjamin W. WycheAtt0rneyTeagno & Toddy 57 ABSTRACT A drive for transmitting torque froma driving to a driven member includes an inflatable member which isadapted to connect the driving and driven members when inflated by afluid under pressure. The drive includes a valve assembly having aninlet connected to a fluid supply, a first outlet in communication withthe inflatable member and a second outlet for venting the inflatablemember. The valve assembly has a movable one-piece valve member whichhas a first position for restriciting fluid flow between the inlet andthe first and second outlets while providing for fluid communicationbetween the first and second outlets. When fluid is supplied underpressure to the inlet, the valve member has a surface area against whichthe fluid acts to move the valve member from the first position to asecond position. In the second position, the valve member restrictsfluid flow between the first and second outlets while providing forfluid communication between the inlet and the first outlet which effectsinflation of the inflatable member, resulting in the driving and drivenmembers being drivingly connected thereby. A muffler may be utilized inconnection with the second outlet to control the level of noiseassociated with the operation of the valve.

6 Claims, 3 Drawing Figures 52c 59 4e 5s 48 470 4? Patented May 22, 19733,734,258

2 Sheets-Sheet 1 INVEN TOR ELM 000 L. R005 A TTORNEYS Patented May 22,1973 2 Sheets-Sheet 2 INVENTOR ELWOOO L. R008 ATTORNEYS COUPLING WITHQUICK RELEASE VALVE BACKGROUND OF THE INVENTION The present inventionrelates to a drive for drivingly connecting relatively rotatable drivingand driven members by means of a fluid actuated clutch or to a brake forstopping a relatively rotating member by means of a fluid actuatedbrake. Particularly the invention relates to a fluid actuated clutch orbrake of the inflatable member type, and more particularly relates to adrive having a valve assembly for supplying fluid under pressure to theinflatable member.

A drive having an inflatable member for drivingly connecting relativelyrotatable driving and driven members is known. Such a drive includes avalve assembly for controlling the fluid flow to the inflatable member.An example of such a drive is shown in Eakin US. Pat. No. 2,879,868.When fluid pressure is supplied to the valve assembly, it is allowed toflow through the valve assembly into the inflatable member. The fluidpressure expands the inflatable member to effect a driving connectionbetween the driving and driven members. When fluid pressure is no longersupplied to the valve assembly, fluid is exhausted from the inflatablemember through the valve assembly such that the driving and drivenmembers are no longer drivingly connected. Thus, it may be seen that thedriving connecting may be effected by supplying the valve assembly withfluid under pressure. On the other hand, such a drive will automaticallydisengage the driving and driven members when pressurized fluid is notsupplied to the valve assembly.

The valve assemblies of the prior art, designed to function in theafore-mentioned manner, have a considerable number of parts and requirea considerable number of machining operations in manufacture. Thesemachining operations are required in order to maintain alignment of themovable valve members with respect to the valve body. If there aremachining errors in these prior art devices, the valve member would notoperate properly thus creating a malfunction in the drive with which itwas used. A further requirement of the prior art devices is closetolerance machining operations. If certain close tolerances are notheld, the valves cannot provide effective sealing of the fluid.Moreover, the simplicity of the present invention provides a long lifefor the valve assembly. The present invention overcomes the above-notedproblems of the prior art by providing a valve assembly having few partsand which may be readily machined. Moreover, the valve assembly of thepresent invention includes a sliding valve member which is maintained inalignment with the valve body by means of a tapered portion of thesliding valve member which mates with a tapered opening in the valvebody. This construction eliminates the need for special machiningoperations required in order to maintain alignment of the valve memberwith respect to the valve body. In addition, the present inventionprovides a valve member which presents a substantial area to the fluidunder pressure when the fluid pressure exceeds a predetermined level.This allows the valve member to stay in a position wherein thepressurized fluid is supplied to the inflatable member.

An object of this invention is to provide a new and improved fluidactuated clutch or brake.

Another object of the present invention is the provision of a new andimproved drive having driving and driven members and an inflatablemember for drivingly connecting the members, and wherein the inflationof the inflatable member is controlled by a valve assembly of asimplified design which may be readily manufactured and is extremelydurable.

It is a further object of the present invention to provide a new andimproved drive having driving and driven members and an inflatablemember for drivingly connecting the members, and wherein the inflationof the inflatable member is controlled by a valve assembly having avalve member in the form of a slidable member.

It is a further object of this invention to provide an improved valveassembly for operating a fluid actuated device.

It is another object of the present invention to provide a new andimproved drive having driving and driven members and an inflatablemember for drivingly connecting the members, and wherein the inflationof the inflatable member is controlled by a valve assembly having aninlet and an outlet and wherein a movable valve member is maintained inalignment with the valve inlet and outlet by means of a tapered memberprotruding from the valve member and slidably received in an opening inthe valve body.

It is yet another object of the present invention to provide a new andimproved drive having driving and driven members and an inflatablemember for drivingly connecting the members and wherein the inflation ofthe inflatable member is controlled by a valve assembly which requires aminimum amount of machining.

It is a further object of the present invention to provide a new andimproved drive having driving and driven members and an inflatablemember for drivingly connecting the members and wherein the inflation ofthe inflatable member is controlled by a valve assembly having an inletand first and second outlets and a valve member operable in the positionto connect the inlet with the first outlet while sealing the firstoutlet from the second outlet and operable in another position to sealthe inlet from the first outlet and communicate the first outlet withthe second outlet.

It is a further object of the present invention to provide a new andimproved device having a valve with a fail-safe mode of operation.

Further objects, advantages, and features of the present invention willbe apparent to those skilled in the art to which it relates from thefollowing detailed description thereof made with reference to theaccompanying drawings forming a part of this specification and in which:

FIG. 1 is a fragmentary sectional view of a drive having a driving anddriven member adapted to be drivingly connected by an inflatable memberand embodying the immediate invention;

FIG. 2 is a sectional view showing the valve assembly of the presentinvention with parts in one position;

FIG. 3 is a sectional view of the valve assembly of FIG. 2 showing partsin another position.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides anew and improved drive for drivingly connecting relatively rotatabledriving and driven members by means of an air actuated clutch includingan inflatable member. While an air actuated clutch of the inflatablemember type is used for illustrative purposes, it is understood thatother air actuated devices, such as air piston clutches or brakes anddiaphragm clutches or brakes are equally suitable applications for thepresent invention. A valve assembly is connected to the inflatablemember for supplying fluid under pressure to the inflatable member suchthat the inflatable member may be inflated to drivingly connect thedriving and driven members. The immediate invention simplifies the valveassembly and minimizes the amount of machining required to manufacturethe valve assembly without detrimentally affecting the operationalcharacteristics of such a valve. One such drive system isrepresentatively shown in FIG. 1 in connection with a press fordrivingly connecting the driving and driven members of the press.

The press 10 has a driving member 12 and a driven member 16 which aremounted so that they are relatively rotatable. A resiliently inflatablemember 40 is provided for drivingly connecting the driving and drivenmembers 12, 16, respectively. A valve assembly 32 is provided forsupplying fluid under pressure to the inflatable member 40. When fluidpressure is supplied to the inflatable member 40, the driving member 12is connected to the driven member 16 such that torque is transmittedtherebetween. When the fluid pressure is exhausted from the inflatablemember 40, it deflates, and, consequently, torque transmission from thedriving member 12 to the driven member 16 is terminated.

The driving member 12 of the press 10 is connected to a motor (notshown) by means of a plurality of belts. The motor rotates at a constantspeed and drives the driving member which is in the form of a flywheel.The press 10 includes a crankshaft 15 to which the driven member 16 isdrivingly connected. The crankshaft 15 is operatively connected to apress ram such that the press ram will move along a path for performingstandard press functions, as is well known to those skilled in the art,upon rotation of the crankshaft.

When a press operator requires movement of the press ram, a switch istripped by the press operator to supply pressurized fluid to the valveassembly 32. The valve assembly 32 directs the fluid to the inflatablemember 40 such that it is inflated. The inflatable member 40 drivinglyconnects the driving member 12 to the driven member 16 upon inflation toeffect movement of the press ram. When a sufficient number of strokes ofthe press ram have occurred, the press operator terminates the supply ofpressurized fluid to the valve assembly 32. The inflatable member 40then deflates and the driving member 12 and driven member 16 aredrivingly disconnected.

The press 10 also includes a brake 18 which is simultaneously actuatedin conjunction with the disconnection of the members 12, 16 to stop thedriven member 16. The brake 18 is of a conventional construction, wellknown to those in the art, and does not comprise a part of the immediateinvention. Accordingly it will not be described in detail.

The fluid supply is operable to supply a fluid, such as air, underpressure to the valve assembly 32 by means of conduits 20 and 30. Theswitch which is tripped by the press operator is positioned in theconduit 20 to prohibit the supply of pressurized fluid to the valveassembly 32, but operable upon actuation to direct pres-' surized fluidthereto. The conduit 20 is connected to a rotary seal device 22 whichmay be of conventional construction, well-known to those skilled in theart. A conduit 30 is connected to the rotary seal device 22 forsupplying fluid under pressure to the valve assembly The valve assembly32, as seen in FIG. 2, includes a valve body 52 having an inlet 34 and afirst outlet 36 connected with the inflatable member 40. The valve body52 has a second outlet 37 connected with the atmosphere. The inlet 34and outlets 36, 37 communicate with a chamber 49 in the valve body 52.The chamber 49 is adapted to receive a slidable one-piece valve member48. When the valve member 48 is in its first position, as shown in FIG.2, fluid flow from the inlet 34 to the outlet 36 is restricted and anypressurized fluid in the inflatable member 40 is exhausted through theoutlet 37. When the valve member 48 is moved to the second position, asshown in FIG. 3, the fluid flow from the outlet 36 to the outlet 37 isrestricted, and fluid flows from the inlet 34 to the outlet 36 toinflate member 40.

The inflatable member 40 has a friction surface 42 which is adapted uponinflation to engage a complementary friction surface 44 on the drivenmember 16 such that the driving member 12 is drivingly connected to thedriven member 16 thereby. The valve assembly 32 automatically operatesto allow the pressurized fluid in the inflatable member 40 to exhaustthrough the second outlet 37 when fluid pressure is removed from inlet34. As a result, the inflatable member 40 retracts, whereupon thedriving member 12 is no longer drivingly connected to the driven member16.

As shown in FIG. 2, the valve body 52 includes a body member 52a and aplug member 52b suitably secured in the valve body 52a as by a threadedconnection 52c therebetween. Biasing means 42, such as a spring, areprovided to maintain the valve member 48 in a position blockingcommunication between inlet 34 and either outlet when pressurized fluidis not supplied to the inlet 34. The biasing means acts between the plugmember 52b and a spring seat 47 on the valve member 48. Spring seat 47may additionally include a wear ring 47a to reduce the wear between theseat 47 and spring 46. Valve member 48 includes a smaller diameterportion 50 which is sealingly engaged by and slidably disposed within abore 51 of the valve body 52. Adjacent the smaller diameter portion 50is a flanged section 53. Flanged section 53 is sealingly and slidablyengaged by interior walls 56 of valve body 52 which define chamber 49.Flange 53 includes a tapered section portion 53a. The valve member alsohas an axial bore 54 extending partially therethrough. A plurality ofradial bores 55 communicate the axial bore 54 with the exterior ofsmaller diameter portion 50, axial bore 54 opens to inlet 34. In theposition shown in FIG. 2, radial bores 55 are maintained in sealingcontact with valve body bore 51 and valve member flange 53 seals chamber49 from inlet 34.

Adjacent the flange section 53 of valve member 48 is a tapered section57 which extends towards the second outlet 37 of the valve body 52. Thesecond outlet 37 is equipped with an annular valve seat 59 which isgenerally concave to readily mate with tapered section 57 eliminatingthe requirement for precise and expensive'machining to assure perfectalignment. Second outlet 37 communicates with the atmosphere and mayinclude a muffler 70. Annular valve seat 59 may be of rubber or othersuitable sealing materials.

It should be noted that muffler 70 may be formed as an integral part ofplug member 52b. The muffler should be of the type which is highlyefficient in reducing noise level while offering a minimum obstructionto exiting air. A muffler with a plurality of baffles 71 in theairstream 72 and normal thereto has been found to be very effective forthis application.

When fluid is supplied to the inlet 34 with sufficient pressure to movethe member 48 with respect to the spring biasing means 46, the valvemember 48 moves to the position shown in FIG. 3. The first effectivearea of the valve member 48 presented to the inlet 34 prior to movementis generally designated at 64, and is defined by the interior of bore54. As the valve member 48 moves sufficiently away from the fluidsealing bore 54 to allow radial bores 55 to communicate with valvechamber 49, a second area generally indicated at 66, is presented to thefluid pressure in the inlet 34. This second area 66 is equal to the areaof the member 48 defined by the major diameter of the valve member 48minus the area defined by smaller diameter portion 50.

When a predetermined amount of fluid pressure is applied through theinlet 34 to the first area 64 of valve member 48, the biasing means isovercome and the valve member 48 moves toward the second position, asshown in FIG. 3. Fluctuations in fluid pressure supply to the inlet 34will not allow the valve member 48 to return to the position shown inFIG. 2, since the second area 66 of the valve member 48 is greater thanthe first area 64. It is only when the fluid pressure drops below thepredetermined level required to move it from the first position that thevalve member 48 will return to the first position.

When the valve member 48 moves to the position of FIG. 3, the taperedsurface 57 engages valve seat 59 and seals first outlet 36 from fluidcommunication with second outlet 37. When the valve member 48 is in thisposition, fluid flows from the source of pressurized fluid into inlet34; through bore 51 into axial bore 54, through radial bores 55 intochamber 49 past flange 53 out the outlet 37 to inflatable member 40.

When the fluid pressure in the inlet 34 is removed, the biasing spring46 and the pressure of exiting fluid from the inflatable member 40acting on the tapered portion 53a of flange 53 quickly move the valvemember 48 to the right, sealing radial bores 55 in bore 51 thus blockingthe inlet 34. Because of this movement of the valve member 48, the firstoutlet 36 is communicated with second outlet 37. As a result, fluid inthe inflatable member 40 exhausts through outlet 36, chamber 49 in thevalve body 52, and outlet 37. This results in deflation of theinflatable member 40.

It should be noted that the pressure of fluid exiting from inflatablemember 40 acting upon tapered surface 57 and 53a is sufficient to shiftthe valve member 48 to the right in the event of a failure of spring 46.This features provides a reliable fail safe mode of operation for valvemember 32.

The valve assembly 32 as should be apparent from the above, has aminimum of parts and requires a minimum of machining as compared withthe known valve assemblies for performing the functions of valveassembly 32. The valve 32 is operative so that when sufficient fluidpressure is supplied thereto, the inflatable member 40 is quicklyinflated and the driving and driven members l2, 16, respectively, aredrivingly connected. When the fluid pressure is removed, the valveassembly 32 is operative to allow the fluid in the inflatable member tobe quickly discharged therefrom such that the driving and driven membersare no longer drivingly connected.

The valve assembly 32 of the immediate invention includes a valve body52 having an inlet 34 connected to the fluid supply, a first outlet 36in communication with the inflatable member 40 and a second outlet 37.When the valve member 48 is in a first position, the fluid in theinflatable member 40 is free to discharge therefrom so that the drivingand driven members 12, 16, respectively are disengaged. When sufficientpressure is supplied to the inlet 34, the valve member 48 moves to asecond position which restricts flow from the inflatable member 40 fromthe first outlet 36 through the second outlet 37. The fluid pressuresupplied through inlet 34 flows through the first outlet 36 to expandthe inflatable member and drivingly connect the driving member 12 to thedriven member 16.

Having thus described my invention, I claim:

1. A drive comprising relatively rotatable driving and driven members,one of said members carrying a resiliently inflatable member which uponapplication of pressurized fluid drivingly connects said driving anddriven members, a valve assembly in fluid communication with saidresiliently inflatable member, said assembly including a valve bodyhaving an inlet connected to a supply of pressurized fluid, a firstoutlet in communication with said inflatable member, a second outlet,and a one-piece valve member, said valve body having a substantiallystraight bore therethrough, said bore having reduced diameter portionsat the opposite ends thereof for defining in substantially coaxialrelationship of said inlet and said second outlet, said valve memberbeing slidably and sealingly mounted in said bore, said valve memberhaving a first position for restricting fluid flow between said inletand said second outlet while providing for fluid communications betweensaid first and second outlets, said valve member having a surface areaagainst which fluid from said fluid supply acts to move said valvemember to a second position for restricting fluid flow between saidfirst and second outlets while providing for fluid communication betweensaid inlet and said first outlet to thereby reflect inflation of saidresilient member to establish a drive between said driving and drivenmembers, said valve assembly including biasing means for maintainingsaid valve member in said first position when the fluid pressure fromsaid fluid supply is below a predetermined level, said valve memberhaving an inner bore defining a first area in communication with inletfluid when said valve member is in said first position and an exteriorflange defining a second area of greater area than said first area incommunication with inlet fluid when said valve member is in said secondposition, said exterior flange having a tapered area opposed to saidsecond area, fluid pressure acting upon said tapered area beingeffective to move said valve member from said second to said firstposition, said valve member supporting a tapered member adapted to beslidably received in said second outlet to maintain said valve member incoaxial relation with said bore when said valve member is in said secondposition.

2. The drive of claim 1 wherein said inflatable member is a resilientinflatable member, the pressure of fluid exhausting from said resilientinflatable member acting upon said tapered area being sufficient to movesaid valve member to its first position in the event of failure of saidbiasing means.

3. The apparatus of claim 2 wherein said second outlet includes a soundmuffling device to muffle the sound of exhausting fluids.

4. In a drive having relatively rotatable driving and driven memberswith one of said members carrying an inflatable member which uponinflation drivingly connects said driving and driven members, a valveassembly in fluid communicates with said inflatable member, said valveassembly including a valve body having an inlet for connection to asupply of fluid, a first outlet in communication with said inflatablemember, a second venting outlet, and a one-piece valve member, saidvalve body having a bore therethrough defining said inlet and saidsecond outlet at the opposite ends thereof, said valve member beingslidably mounted in said bore and having a first position forrestricting fluid flow between said inlet and said second outlet whileproviding for fluid communication between said first and second outletsto vent said inflatable member and a second position for restrictingfluid flow between said first and second outlets while providing forfluid communication between said inlet and said first outlet to effectinflation of said inflatable member to establish a drive between saiddriving and driven members, said valve member comprising a generallycylindrical section, a flanged section, and a tapered section, saidvalve member defining a first surface area against which fluid from saidfluid supply acts to move said valve member to said second position anda second surface area of greater area than said first area, said secondsurface area exposed to fluid pressure only when said valve member is inthe second position, fluid pressure acting upon said second area beingeffective to maintain said valve member in said second position, saidvalve assembly including biasing means urging said valve member to itssaid first position.

5. The drive of claim 4 wherein said valve members cylindrical sectionis axially slidable and sealingly engaged in said valve body boreadjacent said inlet, said cylindrical section having an axial boretherein for communication with said inlet, and a plurality of radialbores communicating said axial bore with the surface of said cylindricalsection.

6. The drive of claim 5 wherein said radial bores are sealingly engagedby said bore in said first position and said radial bores are in fluidcommunication with said first outlet in said second position. l l

w 2 3 Write STATES mrrnr entree CERTEFECATE @E QQRREC'NQN Patent NO-Dated y 9 Inventofls) Elwood L. Roob It is certified that error appearsin the above-identified patent and that said Letters Patent are herebycorrected as shown below:

Col. 5, line 14: Delete "interior of bore 54" and insert -area incross-section of bore 5l--.

Col. 5, line 21: After 50. insert-Second area 66 has an opposing area onthe opposite side of flange 53a which will not be exposed to inletpressure until such time as inlet 34 is in fluid communication withoutlet C01. 5, line 28: Before "second" insert---area opposing---.

Col. 5, line 29: After "48" delete "is greater than the first area 64"and insert---will not be exposed to inlet pressure as the valve member48 moves sufficiently towards the inlet 34 to block fluidcommunicationbetween the inlet 34 and the outlet 36, thus at thisposition rendering second area 66 exposed to inlet pressure andeffectively unopposed- -a 7 Col. 5, line 30: Before "fluid"insert-inlet-- After "drops" insert-esignificantly-.

Col. 5, line 31: Delete "it" and insert----valve member 48-'--.

Claim 4, Col. 8, line 9: Delete "in the" and insert ---moved towardsaid-re, 7 7 L. .9

PO-1O5O UNITED STATES PATENT @FFKCE 56 CERTIFICATE OF CURREGNGN PatentNo. 3,734,258 Dated May 22, 1973 Inventor) Elwood L. Roob Page 2 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

line 10: Delete "maintain" insert---prevent---.

line ll: I Delete "in said second position, and

insert---from moving from said second to said first position as a resultof mere momentary fluctuations in-supply fluid pressure,--.

Signed and sealed this 19th day of February 19714..

(SEAL) Attest:

EDWARD M.FLETCHER ,JR. C. MARSHALL DANN Commissioner of PatentsAttesting Officer

1. A drive comprising relatively rotatable driving and driven members,one of said members carrying a resiliently inflatable member which uponapplication of pressurized fluid drivingly connects said driving anddriven members, a valve assembly in fluid communication with saidresiliently inflatable member, said assembly including a valve bodyhaving an inlet connected to a supply of pressurized fluid, a firstoutlet in communication with said inflatable member, a second outlet,and a one-piece valve member, said valve body having a substantiallystraight bore therethrough, said bore having reduced diameter portionsat the opposite ends thereof for defining in substantially coaxialrelationship of said inlet and said second outlet, said valve memberbeing slidably and sealingly mounted in said bore, said valve memberhaving a first position for restricting fluid flow between said inletand said second outlet while providing for fluid communications betweensaid first and second outlets, said valve member having a surface areaagainst which fluid from said fluid supply acts to move said valvemember to a second position for restricting fluid flow between saidfirst and second outlets while providing for fluid communication betweensaid inlet and said first outlet to thereby reflect inflation of saidresilient member to establish a drive between said driving and drivenmembers, said valve assembly including biasing means for maintainingsaid valve member in said first position when the fluid pressure fromsaid fluid supply is below a predetermined level, said valve memberhaving an inner bore defining a first area in communication with inletfluid when said valve member is in said first position and an exteriorflange defining a second area of greater area than said first area incommunication with inlet fluid when said valve member is in said secondposition, said exterior flange having a tapered area opposed to saidsecond area, fluid pressure acting upon said tapered area beingeffective to move said valve member from said second to said firstposition, said valve member supporting a tapered member adapted to beslidably received in said second outlet to maintain said valve member incoaxial relation with said bore when said valve member is in said secondposition.
 2. The drive of claim 1 wherein said inflatable member is aresilient inflatable member, the pressure of fluid exhausting from saidresilient inflatable member acting upon said tapered area beingsufficient to move said valve member to its first position in the eventof failure of said biasing means.
 3. The apparatus of claim 2 whereinsaid second outlet includes a sound muffling device to muffle the soundof exhausting fluids.
 4. In a drive having relatively rotatable drivingand driven members with one of said members carrying an inflatablemember which upon inflation drivingly connects said driving and drivenmembers, a valve assembly in fluid communicates with said inflatablemember, said valve assembly including a valve body having an inlet forconnection to a supply of fluid, a first outlet in communication withsaid inflatable member, a second venting outlet, and a one-piece valvemember, said valve body having a bore therethrough defining said inletand said second outlet at the opposite ends thereof, said valve memberbeing slidably mounted in said bore and having a first position forrestricting fluid flow between said inlet and said second outlet whileproviding for fluid communication between said first and second outletsto vent said inflatable member and a second position for restrictingfluid flow between said first and second outlets while providing forfluid communication between said inlet and said first outlet to effectinflation of said inflatable member to establish a drive between saiddriving and driven members, said valve member comprising a generallycylindrical section, a flanged section, and a tapered section, saidvalve member deFining a first surface area against which fluid from saidfluid supply acts to move said valve member to said second position anda second surface area of greater area than said first area, said secondsurface area exposed to fluid pressure only when said valve member is inthe second position, fluid pressure acting upon said second area beingeffective to maintain said valve member in said second position, saidvalve assembly including biasing means urging said valve member to itssaid first position.
 5. The drive of claim 4 wherein said valvemember''s cylindrical section is axially slidable and sealingly engagedin said valve body bore adjacent said inlet, said cylindrical sectionhaving an axial bore therein for communication with said inlet, and aplurality of radial bores communicating said axial bore with the surfaceof said cylindrical section.
 6. The drive of claim 5 wherein said radialbores are sealingly engaged by said bore in said first position and saidradial bores are in fluid communication with said first outlet in saidsecond position.